Modification of road bitumens with thermoplastic polymers

Abstract

Polymer modified bitumens were prepared by blending bitumens with different thermoplastic polymers (SBS, SEBS, EVA and EBA). The fundamental properties (e.g. morphology, rheology and ageing) of the modified binders were studied using fluorescence microscopy, dynamic mechanical analysis, creep test (bending beam rheometer), and gel permeation chromatography. The results indicated that the morphology and rheological properties of the modified binders were influenced by characteristics and content of the polymer and nature of the bitumen. When a continuous polymer phase was formed at a sufficiently high polymer content (about 6%), the rheological properties of the binders were improved significantly. At a given polymer content, the modified binders containing SBS and SEBS differ widely from those containing EVA and EBA in their rheological behavior. The ageing properties of the binders were also strongly dependent on types of polymer. In most cases, the rheological changes during ageing were related to oxidation of bitumen and/or degradation of polymer. In addition, the effect of ageing was testing condition (e.g. temperature) dependent.